Haruhiko Takase

Guidance of Divertor Channel by Cusp-Like Magnetic Field for Tokamak Devices

A divertor magnetic configuration is proposed that significantly reduces heat load on the divertor plates in tokamak devices. The proposed configuration utilizes an additional cusp-like magnetic fi...

DT-DD Hybrid Pellet for Inertial Confinement Fusion

A proposal here for inertial confinement fusion is to make use of a hybrid pellet with DT and DD. The spherical pellet consists of two layers of an inner DT and an outer DD. Alpha particles released from the inner layer due to DT reactions heat the DD fuel and induce reactions in the outer DD layer. Numerical simulations by using a hydrodynamic code make clear the following two facts: 1) The output fusion energy due to DD reactions can exceed the stored energy in the compressed pellet. 2) The critical value of ρ R is about 50 for the enough output fusion energy to a reactor.

Tritium Breeding in DT–DD Hybrid Pellet for Inertial Confinement Fusion

The phenomenology of thermonuclear burn with a secondary reaction is investigated by using a method of numerical simulation for a DT-DD hybrid pellet with a high density. The simulation is carried out by use of a one-dimensional hydrodynamic Lagrangian code, showing the capability of tritium breeding in the hybrid pellet. The breeding ratio in the pellet is clarified to be able to exceed unity when the following two conditions are satisfied. 1) The amount of tritium is remarkably less than the amount of deuterium initially stored in the pellet, so that the amount of tritium produced by DD reactions is beyond the initial amount of tritium. 2) The pellet has a so high temperature and a so high ρ R , that the amount of tritium does not decrease anomalously through the secondary DT reaction, because the rate of DT reactions decreases as the temperature increases above 70 keV.

Power plant design study of a high aspect ratio Tokamak using a SiC composite structure

Abstract The DREAM (DRastically EAsy Maintenance) Tokamak is a fusion power plant which is designed from the viewpoint of maintenance feasibility. For this purpose, the DREAM reactor uses a plasma with a very high aspect ratio (A) and adopts SiC as a structural material. The choice of SiC affects the design of the core plasma, i.e. large inboard shield thickness, low synchrotron radiation reflectivity, and small plasma elongation for positional stability. The objectives of this study are to explore the feasibility of a high-A device, such as a power plant, and to clarify the technological impact of SiC material on the plasma design. Plasma size is optimized by the physics guidelines similar to ITER. The plasma major and minor radii of DREAM are 16 m and 2 m, respectively, and the average neutron wall load is 2.5 MW m−2, the maximum toroidal field is 20 T, and the fusion power is 5.5 GW. Steady-state operation is obtained with 50 MW of external current-drive power and 90% bootstrap current. The divertor heat load is estimated to be about 10 MW m−2. A radiative divertor concept is adopted to achieve a low divertor plasma temperature. The DREAM Tokamak concept is found to be a possible candidate for a future power plant with more than 5 GW of fusion power and an acceptable divertor condition.

Numerical Simulations of Lower Hybrid Current Drive by the (1+2)-Dimensional Fokker-Planck Code Combined with the Ray-Tracing Code

The (1+2) dimensional (1-D in real space and 2-D in momentum space) relativistic Fokker-Planck code combined with the ray-tracing code has been newly developed for analyzing the lower hybrid current drive (LHCD) on tokamak plasmas. This numerical code calculates the 2-D MHD equilibrium, ray-tracing, and Fokker-Planck analyses self-consistently. The simulations have been carried out by using the code, and the results were compared with experiments on the lower hybrid current drive in JT-60. As a result, the obtained simulation results agreed with the experimental results on the current drive efficiency and the current density profile ( or the plasma internal inductance).

Effects of Second Order Terms in Amplitudes on Analysis of Particle Tracking for Small Circular Storage Rings

In the analysis of particle tracking for small circular storage rings, the equation of motion with perturbation terms up to the second order in betatron amplitude is derived by assuming a one-dimensional simple model and the effects are estimated in this paper. The difference of betatron number between the equation of motion with perturbation terms up to the second order and that up to the first order becomes increase, when the magnetic field index is larger than 0.6.